Improvement in rock-drills



' MILAN C. BULLOCK.

K Improvement in Rock Drills.

No.4 122,514.` Y Patentedlamwsz.

Rg. 1. y

PATENT OFFICE.

MILAN C. BULLOGK, 0F NEW YORK, N. Y.

IMPROVEMENT IN RQCK-DRILLS.

Specification forming part of Letters Patent No. 122,514, dated January 9, 1872.

invention, reference being had to the accompanying drawing which forms a part of thisl specification, and in which- Figure 1 is a side elevation of my improvement 5 Fig. 2, a vertical section; and Fig. 3, a bottom view thereof. Figs. 4 and 5 are vertical sections of different modifications.

The same parts are denoted bythe same letters in all the figures.

My invention relates to the revolving bit or boring head of a diamon l-drill, and is especially applicable to that class of diamond drillheads which are made solid, so as to excavate a circular hole; although it may also be applied to the annular drill.

111 the solid bit, now commonly in use, the cutting end, on which the diamonds are arranged, is made pointed or conical. The point or apex of the bit is thus not only the point of a wedge which enters the rock, but also the pivot upon which the drill revolves, and is, consequently, subjected to the heaviest crushing strain of any part of the bit, whiie at the same time it has hardly any motion from the revolution of the drill. Thus the center dia- I mond, which is practically a dead-center, and

has the least motion to do the work with, is made to do the hardest part of the Work. My invention is designed to remedy this defect; consists in making the end of the bit concave instead of convex.

t A, in the drawing, represents the bit or borlng head of a diamond-drill, upon Whose reentrant conical surface, shown in section in Fig. 2, are arranged the diamonds B B. The consequence of this construction is, that the Work of penetration is entirely performed by the outer or clearance diamonds, which, being set in the periphery of the bit, have the greatest amount of motion to do the work with, while the inside cone has only to cut away the core of' rock, the amount of work required of each diamond being proportional to its amount of motion, and the center diamond having only to crumble oft' the apex of the core, instead of forcing an entrance into the rock. C is a small central hole communicating with the hollow drill-rod for the purpose of supplying water to lubricate the bit and wash out the detritus. Other holes, D D, may also be made in the bit for the same purpose.

Figs. 4 and 5 show different modes of constructin g my improved bit in sections. The rings E E are slipped one inside of another, and by replacing one or more of them with rings of diiierent width or thickness, the inside angle ofthe bit may be made sharper or more obtuse, as may be desired, for diii'erent kinds of rock. This construction is also advantageous if a diamond should break, as in. such case the ring on which the broken diamond is may be at once replaced.

I have described this invention as applied only to a solid bit; but it is also useful when applied to an annular one, although not in the same degree.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

The above-described concave diamond bit or boring-head.

M. C. BULLOCK.

Witnesses:

SAM. E. GRIsooM Tnos. A. BURTT. (124) 

